JP5884824B2 - Engine stop control device for hybrid vehicle - Google Patents

Description

  The present invention relates to an engine stop control device for a hybrid vehicle including a direct injection engine.

  (a) a direct injection engine that directly injects fuel into the cylinder; (b) a clutch that connects and disconnects (connects and disconnects) the direct injection engine to the power transmission path; and (c) functions as at least an electric motor. And (d) a hybrid vehicle that can use the direct injection engine and the rotating machine as a driving force source for traveling. The hybrid vehicle described in Patent Document 1 is an example, and a friction clutch is connected (friction engagement) during motor traveling that uses only the rotating machine as a driving force source to rotate the crankshaft of the direct injection engine, and the expansion stroke. An ignition start technique is described in which fuel is injected and ignited into a cylinder in the expansion stroke when the engine is started by adjusting the crank angle of the cylinder to be within a predetermined range. Patent Document 2 relates to an engine-driven vehicle having a direct injection engine. When idling stop (engine stop) is performed when the vehicle is stopped, power generation (rotational load) and throttle control by an alternator is prepared for the next engine start. A technique is described in which the crank angle of the cylinder in the expansion stroke falls within a predetermined angle range in which ignition can be started when the engine is stopped by adjusting the output of the engine.

  In some cases, such as when the friction of a direct-injection engine is small, the engine can be started on its own by just starting the ignition, but if necessary, a clutch can be connected to assist cranking with a rotating machine when starting the engine. Yes, the assist torque can be greatly reduced by starting ignition. As a result, the maximum torque of the rotating machine can be reduced, and the size and fuel consumption can be reduced.

JP 2009-527411 A JP 2005-155549 A

  However, in Cited Document 1, since the clutch is merely connected (friction engagement) for a certain period of time and the crankshaft is rotated while the direct injection engine is stopped, the crank angle cannot be quickly brought within a predetermined range. There was a possibility that it was not in time to start the engine. In Cited Document 2, the stopping position of the crankshaft is adjusted by the rotational load of the alternator. However, in the case of a hybrid vehicle in which the direct injection engine is connected to and disconnected from the power transmission path by the clutch, the clutch is connected by differential rotation. Since the braking cannot be performed only by rotating the crankshaft so as to decrease, the technique described in the cited document 2 cannot be applied to the hybrid vehicle described in the cited document 1 to adjust the crank angle when the engine is stopped.

  Here, although not yet known, according to experiments and research by the present inventors, in the case of an 8-cylinder 4-cycle engine, the crank angle of each cylinder can be shifted by 90 °, and when the engine is stopped, In many cases, the crankshaft is stopped within a range in which two cylinders are in an expansion stroke and can automatically start ignition due to a positional energy relationship due to a pumping action (an action like a spring caused by air compression). The crankshaft sometimes stopped near the compression TDC (Top Dead Center) with a probability of about%. FIG. 8 shows the relationship between the crank angle (0 ° = compression TDC) in the expansion stroke, the positional energy by pumping (pumping energy), and the assist torque required at the start of the calculation. There is a peak of pumping energy when the crank angle, which is the compression TDC, is around 0 °, and the crankshaft stops near the apex due to the balance in the rotational direction and engine friction.

  When the crankshaft stops in the vicinity of the compression TDC in this way, in the case of an 8-cylinder engine, the previous cylinder is still in the expansion stroke when the crank angle is close to 90 °, so the ignition start is possible, but the exhaust immediately Since the valve is opened and the exhaust stroke is performed (for example, around 120 °), sufficient rotational energy cannot be expected, and a large assist torque is required at the time of starting. In the case of a 2-cylinder engine to a 6-cylinder engine, the previous cylinder has already passed through the expansion stroke, so there is no cylinder in the expansion stroke, and ignition start itself is impossible.

  The present invention has been made in the background of the above circumstances, and the object of the present invention is to cut off the clutch during traveling in a hybrid vehicle in which the direct injection engine is connected to the power transmission path by the clutch. When the direct injection engine is stopped, the crankshaft is stopped at a position (crank angle) suitable for starting ignition.

In order to achieve this object, the first invention provides (a) a direct injection engine having a plurality of cylinders and directly injecting fuel into the cylinders, and (b) the direct injection engine with respect to the power transmission path. And (c) a rotating machine that functions as at least an electric motor, and (d) the direct injection engine and the rotating machine can be used as a driving force source for traveling, and the rotation thereof In a hybrid vehicle in which an ignition start is performed to start the direct injection engine by injecting and igniting fuel into a cylinder in which the piston is stopped in the expansion stroke while giving an assist torque by the machine, (e) stop position of the crankshaft based the upon blocking the clutch stops the direct injection engine, the first reacting roll point which is the crank angle when the engine rotational speed becomes zero It estimated, that when the stop position deviates from a predetermined target stopping range suitable for the ignition start is a just time or engine stop its engine stopped, pumping by compression of the air in the cylinder Connection torque that can disengage the crankshaft from the peak of pumping energy generated near the compression TDC in which the piston of any cylinder of the direct injection engine reaches the top dead center after the compression stroke within the time when the action is obtained in, by temporarily connecting the clutch is interrupted once, and wherein the arresting its crankshaft automatically straight later crank angle at which the pumping energy is minimized region.

The second invention is the engine stop control apparatus for a hybrid vehicle of the first invention, the connection process of the clutch, characterized in that the crankshaft within the goals stop delimited to stop.

According to a third aspect of the present invention, in the engine stop control device for a hybrid vehicle according to the first or second aspect of the present invention , the clutch connection process is performed using a connection torque that can overcome the friction of the direct injection engine and rotate the crankshaft. The clutch is disengaged immediately when the crank angle exceeds a predetermined control stop position.

According to a fourth aspect of the present invention, in the engine stop control device for a hybrid vehicle according to the first or second aspect of the present invention , the clutch connection process is performed using a connection torque that can overcome the friction of the direct injection engine and rotate the crankshaft. It is generated only for a predetermined time.

According to a fifth aspect of the present invention, in the engine stop control device for a hybrid vehicle according to any one of the first to fourth aspects, the intake air amount adjusting valve is controlled to open when the clutch is disconnected to stop the direct injection engine. It is characterized by.

A sixth aspect of the invention is the engine stop control device for a hybrid vehicle according to any one of the first to fifth aspects of the invention, wherein the output of the rotating machine is increased when the clutch is temporarily connected.

  In such an engine stop control device for a hybrid vehicle, the clutch that is once disconnected immediately after the engine is stopped or immediately after the engine is stopped is temporarily connected. Therefore, even when the crankshaft is stopped near the compression TDC, the clutch is engaged. When the crankshaft is rotated in this way, it is disengaged from the vicinity of the compression TDC, and the pumping energy is stopped at a low crank angle. That is, since the engine is stopped or just after the stop, the pumping action by the compression of the air in the cylinder is obtained before the air leaks from the cylinder, and the pumping energy is automatically stopped at a low crank angle. The crank angle with low pumping energy overlaps with the crank angle range suitable for ignition start with relatively low cranking assist torque at engine start. It is possible to reduce the assist torque when starting the engine.

In addition, the clutch connection process is performed within a time period during which the pumping action by the compression of air in the cylinder is obtained, and the crankshaft is automatically stopped at a crank angle with low pumping energy. Ignition start can be performed appropriately. That is, the amount of air in the cylinder varies depending on the opening of the intake air amount adjustment valve (such as a throttle valve) when the engine is stopped, and when the direct injection engine is stopped with the intake air amount adjustment valve open, Sufficient air is sucked into the cylinder, so a pumping action can be obtained for a relatively long time. However, if the direct injection engine is stopped with the intake air amount adjustment valve closed, the amount of intake air in the cylinder Since the pumping action is lost in a relatively short time due to air leakage, it is necessary to rotate the crankshaft by a clutch connection process in a short time in order to stop the crankshaft at a predetermined crank angle with pumping energy. There is.
In that case, in the present invention, the stop position of the crankshaft is estimated based on the turning point when the engine rotation speed becomes zero first, and the stop position deviates from the predetermined target stop range. In this case, it is possible to quickly determine whether or not the stop position of the crankshaft has deviated from the target stop range, and the clutch connection process can be performed within the time when the pumping action is obtained. Can be done appropriately.

In the second invention, since the crank shaft is defined to stop at the target stop range connection process of the clutch (such as connection torque or connection time) suitable for wearing fire starting, appropriately ignition starting at the next engine start It can be carried out. For example, as in the third aspect of the invention, a connection torque capable of overcoming the friction of the direct injection engine and rotating the crankshaft is generated, and the clutch is immediately disconnected when the crank angle exceeds a predetermined control stop position. Thus, the crankshaft can be rotated from the vicinity of the compression TDC and can be stopped within the target stop range in combination with the pumping action. Further, as in the fourth aspect of the invention, by generating a connection torque that can overcome the friction of the direct injection engine and rotate the crankshaft for a predetermined time, the crankshaft is rotated from the vicinity of the compression TDC and It can be stopped within the target stop range in combination with the pumping action.

In the fifth invention, since the intake air amount adjustment valve is controlled to open when the clutch is shut off and the direct injection engine is stopped, sufficient air is drawn into the cylinder to obtain a pumping action for a relatively long time. The crankshaft can be automatically stopped at a crank angle with low pumping energy by the clutch connection process.

In the sixth aspect of the invention, since the output of the rotating machine is increased when the clutch is temporarily connected, the occurrence of shock due to fluctuations in driving force when the crankshaft is rotated with the clutch connected is suppressed.

It is the schematic block diagram which showed the principal part of the control system | strain in addition to the main point figure of the hybrid vehicle to which this invention is applied suitably. It is sectional drawing explaining the direct-injection engine of the hybrid vehicle of FIG. 2 is a flowchart for specifically explaining the operation of an engine stop control means functionally included in the electronic control device of FIG. 1. FIG. 4 is a flowchart for specifically explaining stop position correction control of a crankshaft in step S <b> 9 of FIG. 3. FIG. FIG. 5 is an example of a time chart for explaining changes in operating states of respective parts when engine stop control is performed according to the flowcharts of FIGS. 3 and 4. FIG. FIG. 5 is a diagram showing an example of a map for obtaining a return amount based on a return point in step S8 of FIG. 3 and step R6 of FIG. It is a figure explaining an example of the stop position of the crankshaft which cannot start ignition in the direct injection engine of various numbers of cylinders, and the stop position of the crankshaft which can start ignition. In a direct injection engine with various cylinder numbers, the relationship between the crank angle (0 ° = compression TDC) in the expansion stroke, the positional energy (pumping energy) due to pumping, and the assist torque required at start-up was calculated. It is a figure which shows a result. It is a figure explaining the other Example of this invention, and is a flowchart used instead of FIG. It is a figure explaining another Example of this invention, and is a flowchart used instead of FIG. In view further illustrating another embodiment of the present invention, Ru flowchart der used in place of FIG.

  The present invention is applied to a parallel type or the like hybrid vehicle in which a direct injection engine is connected to a power transmission path by a clutch, and is used in a motor traveling mode in which only a rotating machine is used as a driving force source or during vehicle deceleration. It is applied to engine stop control when stopping a direct injection engine. As the clutch, a single-plate type or multi-plate type friction engagement clutch is preferably used.

  The hybrid vehicle of the present invention can use a direct-injection engine and a rotating machine as a driving power source for traveling, and the rotating machine can alternatively use the functions of both an electric motor and a generator. A motor generator is preferably used. The direct-injection engine is preferably a four-cycle gasoline engine, and is particularly preferably applied to a multi-cylinder engine having four or more cylinders, but can also be applied to a two-cylinder engine or a three-cylinder engine. It is also possible to use another reciprocating internal combustion engine that can start ignition by injecting fuel into a cylinder in an expansion stroke, such as a two-cycle gasoline engine.

When the engine is stopped or immediately after the engine is stopped, the clutch is temporarily connected to rotate the crankshaft. Immediately after the engine is stopped, the pumping action can be obtained. For example, it may be within about 1 second after the engine is stopped. Further, when the engine is stopped, in fact not only when the rotation of the direct injection engine is stopped, it has good even before direct injection engine is completely stopped. The term “temporary” refers to an extremely short time in which the crankshaft can be rotated from the vicinity of the compression TDC to the crank angle where the pumping energy is low when the crankshaft is stopped near the compression TDC. If the crankshaft is rotated by about 5 ° to 10 °, it can be separated from the peak of pumping energy, and thereafter it automatically rotates to a minimum region that becomes a valley of pumping energy. The clutch engagement state may be continued until the minimum pumping energy region is reached.

In the third and fourth inventions, a connection torque that can overcome the friction of the direct injection engine and rotate the crankshaft is generated. This connection torque is slightly larger than the friction of the direct injection engine. The crankshaft is automatically stopped in the minimum region of the pumping energy by swinging or the like when the clutch is disengaged. In the case of a two-cylinder engine or a three-cylinder engine, as shown in FIGS. 8 (a) and 8 (b), the minimum pumping energy region is larger than the expansion stroke (about 0 ° to 120 °), and an engine that can start ignition appropriately. Since the starting assist torque (start assist torque) exceeds the low target stop range, it is unlikely that the crankshaft will return to the target stop range due to swinging. It is desirable to set a small value within a range where the crankshaft can be rotated by overcoming the friction of the direct injection engine. In the case of a four-cylinder engine, a six-cylinder engine, an eight-cylinder engine, or a multi-cylinder engine having a larger number of cylinders, the minimum region of pumping energy is within the expansion stroke (about 0 ° to 120 °). Is likely to enter the target stop range by returning to the minimum region by swinging, and a larger connection torque can be set as compared with a two-cylinder engine or a three-cylinder engine.

In the third invention, the control stop position for disengaging the clutch may be a position where the crankshaft is separated from the peak of the pumping energy, for example, the crank angle is about 5 ° to 10 ° from the compression TDC. It may be cut off when entering the target stop range that can be performed, or may be cut off before the target stop range, such as the magnitude of the connection torque, friction of the direct injection engine, etc. Various aspects are possible in view of the above. In the fourth aspect of the invention, the connecting torque is generated for a certain period of time. At this certain period of time, at least the crankshaft is disengaged from the pumping energy peak, for example, the crank angle is rotated to a position of about 5 ° to 10 ° from the compression TDC. This time may be the time required to enter the target stop range, and is determined appropriately in consideration of the magnitude of the connection torque, the friction of the direct injection engine, and the like. For these control stop positions and for a certain period of time, if the crankshaft is unlikely to return to the target stop range due to rocking, as in a two-cylinder engine or a three-cylinder engine, the crank angle should not pass the target stop range. It is desirable to set a smaller value. Further, it is desirable that the connection torque, the control stop position, and the predetermined time be corrected by learning as necessary so that the crankshaft stops within the target stop range.

  Here, as is clear from FIG. 8 (c), the four-cylinder engine has a relatively wide minimum region of pumping energy and reaches the vicinity of 120 ° which is the boundary of the expansion stroke, and starts at the vicinity of 120 °. The assist torque increases rapidly. For this reason, in order to avoid stopping the crankshaft at around 120 °, the crank angle of the crankshaft does not pass through the minimum region of the pumping energy as in the case of the two-cylinder engine or the three-cylinder engine. The connection torque, the control stop position, and the predetermined time may be set to a small value so that the motor stops within a range of less than or equal to 0 °.

The present invention relates to a case where clutch connection processing is performed when the stop position of the crankshaft when the engine is stopped deviates from a predetermined target stop range, and the stop position of the crankshaft is based on the turning point. since the estimated Te, Ru can quickly determine whether the stop position of the crank shaft deviates from the target stop range. The target stop range is a range of a crank angle at which ignition can be started appropriately, but a range that overlaps with a minimum region of pumping energy is desirable. As is apparent from FIG. 8, in the case of a two-cylinder engine and a three-cylinder engine, for example, compression TDC The range of about 40 ° to 100 ° is appropriate. In the case of a 4-cylinder engine, for example, a range of about 40 ° to 120 ° from the compression TDC is appropriate. In the case of a 6-cylinder engine, for example, a range of about 40 ° to 80 ° from the compression TDC is appropriate. For example, a range of about 30 ° to 60 ° from the compressed TDC is appropriate. In the case if example embodiment the crankshaft is stopped at the mountain of the pumping energy, that is, when the crank angle in a range of about ± 10 ° of the compression TDC, the connection process of the clutch may be carried out.

In the fifth aspect of the invention, the intake air amount adjusting valve is opened and controlled when the direct injection engine is stopped by disengaging the clutch. This is because air is sufficiently sucked in the suction stroke and compressed in the compression stroke. This is to ensure that the pumping action is properly obtained for a while after the engine is stopped, and a certain degree of pumping action can be obtained based on the intake air even when the intake air amount adjustment valve is closed. In implementation, such opening control of the intake air amount adjusting valve is not necessarily required. The intake air amount adjustment valve is desirably controlled to be opened until the crankshaft substantially stops, for example, until the engine rotational speed first becomes 0, and is desirably controlled to be fully opened. The time and the opening amount are appropriately determined. As the intake air amount adjustment valve, an electronic throttle valve, an ISC valve (idle rotation speed control valve), or the like is preferably used.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic configuration diagram including a skeleton diagram of a drive system of a hybrid vehicle 10 to which the present invention is preferably applied. The hybrid vehicle 10 includes a direct injection engine 12 that directly injects fuel into a cylinder and a motor generator MG that functions as an electric motor and a generator as driving power sources for traveling. The outputs of the direct injection engine 12 and the motor generator MG are transmitted from the torque converter 14 which is a fluid transmission device to the automatic transmission 20 via the turbine shaft 16 and the C1 clutch 18, and further to the output shaft 22, the difference It is transmitted to the left and right drive wheels 26 via the dynamic gear device 24. The torque converter 14 includes a lockup clutch (L / U clutch) 30 that directly connects the pump impeller and the turbine impeller, and an oil pump 32 is integrally connected to the pump impeller. It is mechanically driven to rotate by the jet engine 12 and the motor generator MG. Motor generator MG corresponds to a rotating machine.

  In the present embodiment, the direct injection engine 12 is an eight-cylinder four-cycle gasoline engine. As specifically shown in FIG. 2, gasoline (high pressure) is introduced into a cylinder (cylinder) 100 by a fuel injection device 46. Fine particles) are jetted directly. In the direct injection engine 12, air flows into the cylinder 100 from the intake passage 102 via the intake valve 104, and exhaust gas is discharged from the exhaust passage 106 via the exhaust valve 108. When the ignition device 47 is ignited at this timing, the air-fuel mixture in the cylinder 100 explodes and burns, and the piston 110 is pushed downward. The intake passage 102 is connected to an electronic throttle valve 45, which is an intake air amount adjustment valve, via a surge tank 103. From the intake passage 102 to the cylinder according to the opening of the electronic throttle valve 45 (throttle valve opening). The amount of intake air flowing into 100, that is, the engine output is controlled. The piston 110 is fitted in the cylinder 100 so as to be slidable in the axial direction, and is connected to a crankpin 116 of the crankshaft 114 via a connecting rod 112 so as to be relatively rotatable. Along with the reciprocation, the crankshaft 114 is rotationally driven as indicated by an arrow R. The crankshaft 114 is rotatably supported by a bearing in the journal portion 118, and integrally includes a crank arm 120 that connects the journal portion 118 and the crankpin 116.

  In such a direct injection engine 12, the crankshaft 114 is rotated twice (720 °), and the intake stroke, the compression stroke, the expansion (explosion) stroke, and the exhaust stroke are performed. The shaft 114 is continuously rotated. The pistons 110 of the eight cylinders 100 are configured such that the crank angles are shifted by 90 °, in other words, the positions of the crank pins 116 of the crankshaft 114 protrude in the direction shifted by 90 °, and the crankshaft 114 Each time the cylinder rotates 90 degrees, the eight cylinders 100 are exploded and burned in sequence, and a rotational torque is continuously generated. The crankshaft 114 rotates by a predetermined angle from the compression TDC at which the piston 110 reaches the TDC (top dead center) after the compression stroke, and the predetermined angular range θ of the expansion stroke in which both the intake valve 104 and the exhaust valve 108 are closed. When the fuel is stopped, the fuel injection device 46 injects gasoline into the cylinder 100 and ignites it with the ignition device 47, whereby an ignition start in which the air-fuel mixture in the cylinder 100 is exploded and started is possible. . When the friction (friction) of each part of the direct injection engine 12 is small, the direct injection engine 12 can be started only by ignition start. However, even when the friction is large, the start assist when cranking and starting the crankshaft 114 is started. Since the torque can be reduced, the maximum torque of the motor generator MG that generates the assist torque is reduced, and the size and fuel consumption can be reduced. The angle range θ is suitably in the range of about 30 ° to 60 °, for example, and relatively large rotational energy can be obtained by ignition start, and assist torque can be reduced.

  Returning to FIG. 1, a K0 clutch 34 is provided between the direct injection engine 12 and the motor generator MG via a damper 38. The K0 clutch 34 is a single-plate or multi-plate friction clutch that is frictionally engaged by a hydraulic cylinder, and is engaged and released by the hydraulic control device 28. In the present embodiment, the K0 clutch 34 is disposed in the oil chamber 40 of the torque converter 14. It is arranged in an oil bath state. The K0 clutch 34 is a hydraulic friction engagement device, and functions as a connection / disconnection device that connects or disconnects the direct injection engine 12 with respect to the power transmission path. Motor generator MG is connected to battery 44 via inverter 42. Further, the automatic transmission 20 is a stepped automatic transmission such as a planetary gear type in which a plurality of gear stages having different gear ratios are established depending on the disengagement state of a plurality of hydraulic friction engagement devices (clutch and brake). The shift control is performed by an electromagnetic hydraulic control valve, a switching valve or the like provided in the hydraulic control device 28. The C1 clutch 18 functions as an input clutch of the automatic transmission 20 and is similarly subjected to engagement / release control by the hydraulic control device 28.

  Such a hybrid vehicle 10 is controlled by the electronic control unit 70. The electronic control unit 70 includes a so-called microcomputer having a CPU, a ROM, a RAM, an input / output interface, and the like, and performs signal processing according to a program stored in advance in the ROM while using a temporary storage function of the RAM. Do. A signal representing the accelerator pedal operation amount (accelerator operation amount) Acc is supplied from the accelerator operation amount sensor 48 to the electronic control unit 70. Further, from the engine rotation speed sensor 50, the MG rotation speed sensor 52, the turbine rotation speed sensor 54, the vehicle speed sensor 56, and the crank angle sensor 58, the rotation speed (engine rotation speed) NE of the direct injection engine 12 and the rotation of the motor generator MG, respectively. Speed (MG rotational speed) NMG, rotational speed of turbine shaft 16 (turbine rotational speed) NT, rotational speed of output shaft 22 (corresponding to vehicle speed V by output shaft rotational speed) NOUT, TDC for each of eight cylinders 100 (top dead) A signal relating to the rotation angle (crank angle) Φ from the point) is supplied. In addition, various types of information necessary for various types of control are supplied. The accelerator operation amount Acc corresponds to the output request amount.

  The electronic control unit 70 functionally includes hybrid control means 72, shift control means 74, and engine stop control means 80. The hybrid control means 72 controls the operation of the direct injection engine 12 and the motor generator MG, for example, an engine travel mode in which only the direct injection engine 12 travels as a driving power source, or travels using only the motor generator MG as a driving power source. A plurality of predetermined driving modes such as an engine driving mode using both the motor driving mode and the motor driving mode are switched in accordance with the driving state such as the accelerator operation amount Acc and the vehicle speed V. The shift control means 74 controls an electromagnetic hydraulic control valve, a switching valve and the like provided in the hydraulic control device 28 to switch the engagement / disengagement state of the plurality of hydraulic friction engagement devices. These gear stages are switched in accordance with a predetermined shift map with the operating state such as the accelerator operation amount Acc and the vehicle speed V as parameters.

  The engine stop control means 80 stops the direct injection engine 12 at the time of switching from the engine + motor running mode to the motor running mode, at the time of inertia running during the engine + motor running mode or the engine running mode, at the time of deceleration, at the time of stopping, etc. The engine stop means 82, the throttle opening means 84, the crank angle determination means 86, the clutch engagement means 88, and the drive torque compensation means 90 are functionally provided. FIG. 3 and FIG. The signal processing is executed according to the flowchart. FIG. 4 is a flowchart for specifically explaining the stop position correction control in step S9 of FIG. Steps S3 and S4 in FIG. 3 correspond to the engine stop means 82, Steps S5, S6, and S7 correspond to the throttle opening means 84, and Step S8 and Step R6 in FIG. 4 correspond to the crank angle determination means 86. 4 correspond to the clutch engagement means 88, and steps R2 and R5 correspond to the drive torque compensation means 90. The throttle opening means 84 functions as a valve opening control means for controlling the opening of the intake air amount adjustment valve, and the clutch engaging means 88 functions as a connection control means for temporarily connecting the K0 clutch 34.

  In step S1 of FIG. 3, it is determined whether the ignition start basic condition is satisfied. Whether or not the basic conditions for starting ignition satisfy all of them, such as the conditions for performing intermittent operation for turning on (operating) and turning off (stopping) the direct injection engine 12 and that the engine coolant temperature is equal to or higher than a predetermined temperature. Determine whether. If this ignition start basic condition is satisfied, step S2 is executed to determine whether or not the engine stop condition is satisfied. When the engine stop condition is satisfied when the engine stop condition is satisfied, for example, when switching from the engine + motor drive mode to the motor drive mode or during deceleration in the engine drive mode, engine stop control in step S3 and subsequent steps is executed.

  The time t1 in the time chart of FIG. 5 is the time when the engine stop control is started after the determination in step S2 is YES (positive). FIG. 5 is a diagram showing a change in the operating state of each part when the engine stop control is performed due to coasting with the accelerator off during traveling in the engine + motor traveling mode. 12 of the electronic throttle valve 45, which is 0 (fully closed) at time t1 during inertial running. The surge tank pressure is the pressure in the surge tank 103 provided upstream of the intake passage 102. Since the surge tank 103 communicates with the atmosphere via the electronic throttle valve 45, the time during which the electronic throttle valve 45 is fully closed. At t <b> 1, the pressure is reduced from the atmospheric pressure by the air suction action accompanying the rotation of the direct injection engine 12. The crank angle Φ is a diagram showing a change in the crank angle Φ from the compression TDC to 90 ° when the compression TDC is 0 °. The crank angle Φ of the plurality of cylinders 100 that reach the compression TDC at 90 ° intervals is continuously shown. It is the figure shown in. The K0 clutch pressure is the engagement hydraulic pressure of the K0 clutch 34, and is the maximum pressure (line pressure) at time t1 during running in the engine + motor running mode, and the K0 clutch 34 is fully engaged. The K0 clutch pressure corresponds to the engagement torque of the K0 clutch 34, that is, the connection torque that connects the direct injection engine 12 to the power transmission path.

  In step S3 of FIG. 3, the K0 clutch 34 is disconnected to disconnect the direct injection engine 12 from the power transmission path. In the disconnection process of the K0 clutch 34, for example, the K0 clutch pressure is gradually reduced to zero. In step S4, stop processing of the direct injection engine 12 is executed. In this stop process, the fuel injection from the fuel injection device 46 is stopped (fuel cut), and the ignition control of the ignition device 47 is stopped. Thereby, coupled with the fact that the direct injection engine 12 is disconnected from the power transmission path in step S3, the engine rotational speed NE gradually decreases. The disconnection process of the K0 clutch 34 in step S3 and the fuel cut in step S4 may be performed after the fuel cut, but can be performed in parallel at the same time, or the fuel cut may be performed first. If the fuel has already been cut due to accelerator OFF or the like, the fuel cut may be continued. In the next step S5, the electronic throttle valve 45 is controlled to be opened by a predetermined amount. By controlling the opening of the electronic throttle valve 45, the surge tank 103 is communicated with the atmosphere, and the surge tank pressure gradually rises to near atmospheric pressure. As a result, while the direct injection engine 12 is rotating due to inertia, sufficient air flows into each cylinder 100 during the intake stroke.

  In step S6, it is determined whether or not the rotation of the direct injection engine 12 has substantially stopped, specifically, whether or not the engine rotation speed NE has become, for example, about 100 rpm or less. In step S7, the electronic throttle valve 45 is closed and controlled. A time t2 in FIG. 5 is a time when the stop determination of the direct injection engine 12 is made, that is, a time when the determination of step S6 becomes YES. The closing control of the electronic throttle valve 45 in step S7 may be performed immediately, but is performed after a certain delay time so that the closing control is performed after the rotation of the direct injection engine 12 is completely stopped. The electronic throttle valve 45 may be closed and controlled after confirming that the rotation of the direct injection engine 12 has completely stopped.

  In step S8, it is determined whether or not the stop crank angle Φstop when the rotation of the direct injection engine 12 is stopped is within a predetermined target stop range Φtarget. The engine stop control is terminated as it is, but if it is outside the target stop range Φtarget, stop position correction control in step S9 is executed. The stop crank angle Φstop at this time is determined for, for example, the cylinder 100 within the range of compression TDC ≦ Φstop ≦ compression TDC + 90 °. The stop crank angle Φstop may be the crank angle Φ after the rotation of the direct injection engine 12 is completely stopped, but in this embodiment, the turning point of the crankshaft 114, that is, the engine rotational speed NE first becomes zero. Based on the crank angle Φ at the time, the amount of rocking rcrnk is obtained from a predetermined map as shown in FIG. 6, and a judgment is made using the estimated stop crank angle Φest obtained by subtracting the amount of rocking rcrnk. As a result, it is immediately determined whether or not the stop crank angle Φstop (strictly, the estimated stop crank angle Φest) when the rotation of the direct injection engine 12 has deviated from the target stop range Φtarget, and the stop in step S9. Position correction control can be executed promptly. The stop position correction control in step S9 is to adjust the crank angle Φ using a pumping action (air spring) by the compression of air in the cylinder 100, and the air in the cylinder 100 is transferred from the seal ring of the piston 110 or the like. If the pressure decreases due to leakage, the desired pumping action cannot be obtained. Therefore, the stop position correction control is performed as soon as possible within the time when the pumping action is obtained.

  Further, the target stop range Φtarget is a range of a crank angle Φ that can appropriately start ignition, and overlaps a minimum region of pumping energy. In this embodiment in which an 8-cylinder engine is mounted as the direct injection engine 12, FIG. For example, a range of 30 ° to 60 ° from the compression TDC is determined from the characteristics of the pumping energy and the start assist torque shown in (e) of FIG. The time chart of FIG. 5 shows a case where the stop crank angle Φstop at time t2 is approximately 0 ° and deviates from the target stop range Φtarget. When the turning point is about 0 ° (compression TDC), the amount of turning rcrnk is about 0 °, and the stop crank angle Φstop≈estimated stop crank angle Φest≈0 ° (compression TDC).

  The target stop range Φtarget differs depending on the number of cylinders. In the case of a two-cylinder engine and a three-cylinder engine, for example, a range of about 40 ° to 100 ° from the compression TDC from the characteristics shown in (a) and (b) of FIG. Is appropriate. In the case of a 4-cylinder engine, a range of about 40 ° to 120 °, for example, from the compression TDC is appropriate from the characteristics shown in FIG. 8C. In the case of a 6-cylinder engine, the range shown in FIG. From the characteristics, for example, a range of about 40 ° to 80 ° from the compressed TDC is appropriate. However, in the case of a multi-cylinder engine of 4 cylinders or more, if it is other than the peak of pumping energy, the pumping action (air spring) automatically stops at the valley portion, and if it is the valley portion, the starting assist torque can be reduced to some extent. The target stop range Φtarget may be set large so as to include all the stops at the valleys.

  Here, the pumping energy is potential energy generated by the action of an air spring generated by the air sucked into the cylinder 100 being compressed in the compression stroke. In the case of an 8-cylinder engine, the pumping energy is in the expansion stroke as shown in FIG. In addition to the zeroth cylinder 100 at the crank position indicated by 0 TDC, the first cylinder 100 at the crank position indicated by 1 TDC delayed by 90 °, and the second cylinder 100 at the crank position indicated by 2TDC further delayed by 90 °. Considering the compression and expansion of air, the pumping energy when the crank angle Φ of the zeroth cylinder 100 is 0 ° (compression TDC) to 90 ° is controlled by opening the electronic throttle valve 45 so as to be in each cylinder 100. This is a result obtained by calculation on the assumption that sufficient air flows in at atmospheric pressure. For the two-cylinder engine, the three-cylinder engine, the four-cylinder engine, and the six-cylinder engine, the calculation was performed similarly to the eight-cylinder engine. However, in the six-cylinder engine, the crank angle Φ of each cylinder 100 is shifted by 120 °. As shown in FIG. 7, the first cylinder 100 and the second cylinder 100 at the crank positions indicated by 1TDC and 2TDC are also involved in the compression stroke, and in the 0th to 2nd three cylinders 100 as in the 8-cylinder engine. The calculation was performed in consideration of air compression and expansion. In the four-cylinder engine, the crank angle Φ of each cylinder is shifted by 180 °. Therefore, as shown in FIG. 7, the first cylinder 100 at the crank position indicated by 1 TDC is involved in the compression stroke. Since is not involved in the compression stroke, the calculation was performed in consideration of the compression and expansion of air in the zeroth and first two cylinders 100. In the three-cylinder engine, the crank angle Φ of each cylinder is shifted by 240 °. Therefore, as shown in FIG. 7, the first cylinder 100 at the crank position indicated by 1 TDC is involved in the compression stroke. Since it does not relate to the compression stroke, the calculation was performed in consideration of the compression and expansion of the air in the zeroth and first two cylinders 100 as in the case of the four-cylinder engine. In the two-cylinder engine, the crank angle Φ of the pair of cylinders is shifted to the same position by 360 °, so that only the pressure in the zeroth cylinder 100 at the crank position indicated by 0 TDC is involved in the pumping energy as shown in FIG. The calculation was performed in consideration of the compression and expansion of the air in the zeroth one cylinder 100. In FIG. 7, 0 TDC is a crank position related to the cylinder 100 whose crank angle Φ is 0 ° (compression TDC) or exceeds 0 °, and the crank position of each cylinder 100 subsequent to the cylinder 100 is sequentially set to 1 TDC, 2 TDC. 3TDC,... The broken line shown in the column of the three-cylinder engine represents the crank position of the cylinder 100 delayed by one rotation (360 °) or more. “EVO” is an open position of the exhaust valve 108, and “IVC” is a close position of the intake valve 104.

The start assist torque in FIG. 8 is assist torque required when starting the direct injection engine 12 by ignition start. As shown in the following equation (1), the engine energy of the direct injection engine 12 is determined from the expansion energy obtained by ignition start, the compression energy by the compression of the subsequent cylinder 100, the internal energy such as heat, exhaust, and the like. If the engine energy is positive, the assist torque is not required. If the engine energy is negative, the negative amount is the start assist torque necessary for starting the direct injection engine 12. In this case, it is considered that if the cylinder 100 that enters the compression stroke reaches the compression TDC before the zeroth cylinder 100 passes through the expansion stroke, a stable operation state is assumed. The start assist torque was calculated by calculating the energy until the second cylinder 100 reaches the compression TDC by integration. For the four-cylinder engine and the three-cylinder engine, the energy required until the first cylinder 100 reaches the compression TDC was obtained by integration to calculate the start assist torque. In the two-cylinder engine, there is no cylinder 100 that enters the compression stroke before the zeroth cylinder 100 passes through the expansion stroke, but at least the next cylinder 100, i.e., 1 is used to confirm a stable operation state. Since it is necessary for the first cylinder 100 to reach the compression TDC, the energy until the first cylinder 100 reaches the compression TDC is obtained by integration to calculate the start assist torque. Note that the compression energy of the equation (1) corresponds to the pumping energy.
Engine energy = Expansion energy-Compression energy-Internal energy
-Friction (1)

  The pumping energy and the starting assist torque can be obtained more finely by taking into account, for example, the compression, expansion, discharge, etc. of the air in all the cylinders 100, and specific numerical values are given for each part of the direct injection engine 12. 8 and the opening / closing timing of the intake valve 104 and the exhaust valve 108, etc., it is considered that the general tendency is as shown in FIG. Therefore, for the 8-cylinder engine, the 4-cylinder engine, and the 6-cylinder engine of the present embodiment, the stop crank angle Φstop when the engine is stopped usually enters the minimum region of pumping energy and falls within the target stop range Φtarget. However, a part (for example, about 10%) is a compression TDC, and the crankshaft 114 stops near the top of the pumping energy when the crank angle Φ is around 0 ° by the balance and friction in the rotational direction. The stop position correction control in step S9 is for rotating the crankshaft 114 stopped in the vicinity of the compression TDC from the vicinity of the top of the pumping energy to the minimum region.

  For two-cylinder engines and three-cylinder engines, the stop crank angle Φstop when the engine is stopped usually enters the minimum region of pumping energy, and a part (for example, about 10%) of the crank angle Φ, which is compression TDC, is around 0 °. The crankshaft 114 stops due to rotational balance and friction near the top of the pumping energy. Therefore, if the crankshaft 114 stopped in the vicinity of the compression TDC in this way by the stop position correction control in step S9 is rotated from the vicinity of the top of the pumping energy to the minimum region, it falls within the target stop range Φtarget. The crank angle Φ can be entered. However, as is clear from FIGS. 8A and 8B, the minimum region of the pumping energy is larger than the expansion stroke (about 0 ° to 120 °), and the target stop with a low start assist torque that can start ignition appropriately. Since it exceeds the range Φtarget, it is necessary to perform stop position correction control in step S9 so as not to pass through the target stop range Φtarget. In addition, even if the first stop position, that is, the stop crank angle Φstop is within the minimum pumping energy region, if it passes through the target stop range Φtarget, it cannot be returned to the target stop range Φtarget. Therefore, in this case, the direct injection engine 12 can be reliably started by increasing the assist torque when starting the direct injection engine 12 from the standard value, for example, as in step R7-2 of FIG. You can do that.

  FIG. 7 shows the stop position (stop crank angle Φstop) of the crankshaft 114 that cannot start ignition and the stop position (stop crank angle Φstop) of the crankshaft 114 that can start ignition in the direct injection engine 12 of each cylinder. FIG. 9 is an example based on the characteristics of FIG. In the case of an 8-cylinder engine, the crank angle Φ of the plurality of cylinders 100 is shifted by 90 °, so that the crankshaft 114 of at least one cylinder 100 is within a range where 0 ° (compression TDC) <Φstop <EVO can be started. Thus, ignition can be started regardless of the stop position of the crankshaft 114. In the case of a 6-cylinder engine, the crank angle Φ of the plurality of cylinders 100 is shifted by 120 °. Therefore, as shown in the non-ignition stop position example, the stop crank angle Φstop of the cylinder 100 with 0 TDC is 0 °, that is, compression TDC. , 0 ° (compression TDC) <Φstop <EVO does not exist, and no ignition start is possible, and ignition start is impossible, but other than that, ignition start is possible. In the case of the four-cylinder engine, the three-cylinder engine, and the two-cylinder engine, as shown in the example of the non-ignition stop position, there is an angle region in which there is no cylinder 100 that can be ignited with 0 ° (compression TDC) <Φstop <EVO Yes, ignition start is possible when the stop crank angle Φstop of any cylinder 100 satisfies 0 ° (compression TDC) <Φstop <EVO.

  The stop position correction control in step S9 in FIG. 3 is executed according to the flowchart in FIG. In step R1 of FIG. 4, the engagement hydraulic pressure of the K0 clutch 34 that has been shut off (released) in step S3 is gradually increased to a hydraulic pressure that provides an engagement torque that is larger than the friction of the direct injection engine 12 by a predetermined margin value α. To rise. Time t3 in FIG. 5 is the time when the clutch engagement control in step R1 is started, and the K0 clutch pressure is gradually increased, and reaches the engagement torque of friction + α at time t4. Thus, when the engagement torque of the K0 clutch 34 reaches the friction + α, the crankshaft 114 of the direct injection engine 12 is rotated against the friction. The margin value α may be set in advance in consideration of the compression resistance of the next cylinder 100 or the like, but may be set to a different value using the vehicle speed V or the like as a parameter. It is also possible to perform learning correction based on the rotation state (rotation speed, rotation start hydraulic pressure, etc.) of the crankshaft 114 in consideration of individual differences in friction and changes with time.

  In the next step R2, in order to prevent the drive torque from fluctuating due to the rotational resistance accompanying the rotation of the crankshaft 114 due to the engagement of the K0 clutch 34, the torque (MG torque) TMG of the motor generator MG is applied to the K0 clutch 34. Increase corresponding to the engagement torque. However, in the case where the automatic transmission 20 is at a high gear stage or the like, when the increase width of the MG torque TMG is less than a predetermined allowable value and the vehicle shock hardly occurs, the inertia energy of the vehicle is not increased without increasing the MG torque TMG. Thus, the crankshaft 114 may be rotated. In this case, the consumption of the battery 44 is reduced and the fuel efficiency is improved.

  In step R3, it is determined whether or not the crank angle Φ of the crankshaft 114 is within the target stop range Φtarget. If the crank angle Φ is within the target stop range Φtarget, step R4 and subsequent steps are executed. The time t5 in FIG. 5 is the time when the crank angle Φ is within the target stop range Φtarget and the determination in step R3 is YES, and the lower limit value of the target stop range Φtarget corresponds to the control stop position. In step R4, the K0 clutch pressure is immediately set to 0, and the K0 clutch 34 is immediately disconnected (released). In step R5, the drive torque compensation control (increase in MG torque TMG) by the motor generator MG is performed in accordance with the disconnection of the K0 clutch 34. Control). In step R6, similarly to step S8, it is determined whether or not the stop crank angle Φstop when the rotation of the direct injection engine 12 is stopped is within a predetermined target stop range Φtarget. If it is within the range of Φtarget, a series of stop position correction control ends, but if it is outside the target stop range Φtarget, step R7 is executed. The stop crank angle Φstop at this time may also be the crank angle Φ after the rotation of the direct injection engine 12 is completely stopped, but in this embodiment, based on the turning point of the crankshaft 114, FIG. The amount of rocking rcrnk is obtained from a predetermined map as shown, and the determination is made using the estimated stop crank angle Φest obtained by subtracting the amount of rocking rcrnk. FIG. 5 shows a case where the crankshaft 114 is stopped within the range of the target stop range Φtarget due to rocking. In this case, the determination in step R6 is YES, and the series of stop position correction control ends.

  In a two-cylinder engine or a three-cylinder engine, the crankshaft 114 is unlikely to return to the target stop range Φtarget due to rocking, so that the crankshaft 114 does not pass through the target stop range Φtarget. A control stop position is set in front, that is, on the compression TDC side, and when the crank angle Φ reaches the control stop position, step R4 and subsequent steps are executed to end the engagement control of the K0 clutch 34. In the case of an engine with four or more cylinders including the eight-cylinder direct injection engine 12 of this embodiment, the control stop position is set before the target stop range Φtarget so that the target stop range Φtarget is not passed, and the crank angle Φ When the control stop position is reached, the engagement control of the K0 clutch 34 may be terminated.

  If the determination in step R6 is NO (negative), the margin value α is decreased by a predetermined gradual decrease value β in step R7, and then the steps after step R1 are repeated. If the determination in step R6 is NO, the crankshaft 114 stops outside the target stop range Φtarget, specifically, the crank angle Φ passes through the minimum pumping energy region and rotates to near the top of the next mountain. In this case, the rotation is stopped as it is, and the rotation assist of the crankshaft 114 by the engagement control of the K0 clutch 34 is too large, so the margin value α is reduced and step R1 and subsequent steps are executed again. In steps R3 and R6, a determination is made based on the crank angle Φ of the next cylinder 100 delayed by 90 °. When the determination in step R6 becomes YES, a series of stop position correction control is terminated. However, if the air in the cylinder 100 leaks from the seal ring of the piston 110 and the pressure decreases, the desired pumping action cannot be obtained, and the crank angle Φ correction control cannot be performed properly. If the determination in step R6 is NO even after execution, stop position correction control after step R1 is stopped, and the assist torque for starting the direct injection engine 12 is increased, for example, as in step R7-2 in FIG. What is necessary is just to make it possible to start the direct-injection engine 12 reliably by making it increase from a standard value.

  As described above, in the engine stop control device for the hybrid vehicle 10 of this embodiment, when the direct injection engine 12 is stopped while the vehicle is running, the stop crank angle Φstop or the estimated stop crank angle Φest is within the target stop range Φtarget. In the case of the outside, the K0 clutch 34 once disconnected is temporarily frictionally engaged to rotate the crankshaft 114 a little, so that the crankshaft 114 stopped near the compression TDC reaches the minimum region of the pumping energy valley. Rotate to stop. That is, when the engine is stopped or just after the stop, a pumping action by compression of air in the cylinder 100 can be obtained, and if the crankshaft 114 is rotated by a predetermined angle from the vicinity of the compression TDC located in the peak of pumping energy, the pumping is performed. It is automatically stopped in the minimum region where the energy is low. The crank angle Φ with low pumping energy overlaps with the range of the crank angle Φ suitable for ignition start with a relatively small cranking assist torque at the time of engine start, that is, the target stop range Φ target. An ignition start can be appropriately performed at the time of engine start, and assist torque at the time of engine start can be reduced.

  Further, in the present embodiment, the friction engagement process of the K0 clutch 34, that is, the stop position correction control of FIG. 4 is performed within a time during which the pumping action by the compression of the air in the cylinder 100 is obtained. It is automatically stopped in the minimum region where the energy is low, and the ignition start can be appropriately performed at the next engine start. That is, the air in the cylinder 100 leaks from the seal ring of the piston 110 and the pumping action decreases with the passage of time. In this embodiment, when the direct injection engine 12 is stopped, the electronic operation is continued until the rotation of the crankshaft 114 is stopped. Since the throttle valve 45 is controlled to open, sufficient air is drawn into the cylinder 100 to appropriately obtain a pumping action for a relatively long time, and stop position correction control is performed immediately after the direct injection engine 12 is stopped. The crankshaft 114 is appropriately stopped within the target stop range Φtarget by the pumping action.

  Further, in the present embodiment, the friction engagement process of the K0 clutch 34, that is, the stop position correction control in FIG. 4, is performed with the target stop suitable for ignition start when at least one of the plurality of cylinders 100 of the direct injection engine 12 is in the expansion stroke. Since the crankshaft 114 is stopped in the range Φtarget, the ignition start can be appropriately performed at the next engine start. That is, an engagement torque (friction + α) that can overcome the friction of the direct injection engine 12 and rotate the crankshaft 114 is generated, and the crank angle Φ is a predetermined control stop position (the lower limit of the target stop range Φtarget). Since the K0 clutch 34 is immediately disengaged when the value exceeds the value), the crankshaft 114 can be rotated from the vicinity of the compression TDC and can be stopped within the target stop range Φtarget suitable for ignition start in combination with the pumping action.

  In the present embodiment, the stop position correction control of FIG. 4 is performed when the stop position of the crankshaft 114 at the time of engine stop deviates from a predetermined target stop range Φtarget. Since the stop position is estimated based on the turning point of the crankshaft 114 and the estimated stop crank angle Φest is used to determine whether or not the target stop range Φtarget is deviated, the determination can be made quickly. The stop position correction control of FIG. 4 can be appropriately performed within the time when the pumping action is obtained.

  In this embodiment, an eight-cylinder four-cycle gasoline engine is used as the direct injection engine 12 and is pumped within the expansion stroke range (about 0 ° to 120 °) as shown in FIG. Since there is a minimum region that becomes a valley of energy, the crankshaft 114 is appropriately stopped in the minimum region of the pumping energy by swinging or the like by the stop position correction control of FIG. 4, and the start assist torque is appropriately set by starting ignition. Can be reduced. For a direct injection engine having four or more cylinders, since the minimum region of pumping energy exists within the expansion stroke range (about 0 ° to 120 °), the same effect can be obtained.

  In the present embodiment, when the K0 clutch 34 is temporarily engaged and the crankshaft 114 is rotated, the torque TMG of the motor generator MG is increased according to the engagement torque of the K0 clutch 34 as necessary. Therefore, shocks such as drive torque fluctuations due to the rotational resistance of the crankshaft 114 can be appropriately suppressed.

  Next, another embodiment of the present invention will be described. In the following embodiments, parts that are substantially the same as those in the above embodiments are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 9 is a flowchart used in place of FIG. 4, and a target stop range in which the stop crank angle Φstop (including the estimated stop crank angle Φest) when the rotation of the direct injection engine 12 stops in step R6 is predetermined. Processing after determining whether or not it is within the range of Φtarget is different. That is, if the stop crank angle Φstop is within the target stop range Φtarget and the determination in step R6 is YES, an instruction to use the standard value as the assist torque for cranking at the next engine start is output in step R7-1. However, if the stop crank angle Φstop is outside the target stop range Φtarget and the determination in step R6 is NO, in step R7-2, the cranking assist torque at the next engine start is made larger than the standard value. Outputs an increase instruction. These standard value instructions and increase instructions are output to the engine starting means or the like that is functionally provided in the hybrid control means 72, thereby determining whether or not the crankshaft 114 is within the target stop range Φtarget. The next engine start is always properly performed with an assist torque of an appropriate magnitude.

  The standard value may be a constant value that can be appropriately started using the ignition start when the crankshaft 114 is stopped within the target stop range Φtarget, but as shown in FIG. Since the assist torque varies depending on the crank angle Φ, the crank angle Φ of the crankshaft 114 may be determined as a parameter. Regarding the assist torque due to the increase instruction, it is considered that the crankshaft 114 is basically located at the compression TDC, and therefore a predetermined constant assist torque may be determined in advance.

  FIG. 10 is a diagram for explaining another embodiment, and the engagement process of the K0 clutch 34 is different from that of the embodiment of FIG. That is, in the embodiment shown in FIGS. 4 and 9, it is determined in step R3 whether or not the crank angle Φ is within the target stop range Φtarget. If the crank angle Φ is within the target stop range Φtarget, step R4 and subsequent steps are executed. However, in FIG. 10, step R3-1 is provided instead of step R3, and it is determined whether or not a predetermined time has passed. When the predetermined time has passed, step R4 and subsequent steps are executed to execute the K0 clutch 34. Shut off. This predetermined time is based on the premise that the crankshaft 114 is stopped in the vicinity of the compression TDC, and a certain time during which the crankshaft 114 can be rotated to the minimum pumping energy region against friction or the like is the K0 clutch pressure or the like. Is determined in advance. Therefore, also in this embodiment, the crankshaft 114 can be rotated from the vicinity of the compression TDC and can be stopped within the target stop range Φtarget in combination with the pumping action, and the ignition start is appropriately performed at the next engine start. The same effects as those in the above embodiment can be obtained, such as reduction of the assist torque.

  Here, in the direct-injection engine 12 having four or more cylinders, the minimum region of pumping energy and the target stop range Φtarget substantially coincide with each other, and the crankshaft 114 is returned to the target stop range Φtarget when the rotation of the crankshaft 114 is reversed. As a result, a relatively long time can be set so that the crankshaft 114 can be reliably detached from the vicinity of the compression TDC. In the case of a two-cylinder engine or a three-cylinder engine, since the minimum region of pumping energy exceeds the target stop range Φtarget, it is unlikely that the crankshaft 114 will return to the target stop range Φtarget by swinging, and passes through the target stop range Φtarget. A relatively short time is set so as not to. The fixed time can be learned and corrected so that the crankshaft 114 stops within the target stop range Φtarget. In the flowchart of FIG. 10, as in FIG. 9, when the stop crank angle Φstop is outside the target stop range Φtarget, an instruction to increase the assist torque is output in step R <b> 7-2. Even when the crank angle Φ of the engine passes the target stop range Φtarget, the next engine start can be appropriately performed with an assist torque of an appropriate magnitude.

  In the embodiment of FIG. 4, step R3-1 of FIG. 10 may be performed instead of step R3.

FIG. 11 is a flowchart used in place of FIG. 3, and is different from the embodiment of FIG. 3 in that step S8-1 is provided instead of step S8. That is, in step S8, it is determined whether or not the stop crank angle Φstop of the direct injection engine 12 is within the target stop range Φtarget. If the stop crank angle Φstop is outside the target stop range Φtarget, the stop position correction control in step S9 is executed. In step S8-1 in FIG. 11, it is determined whether or not the stop crank angle Φstop is in the vicinity of the compression TDC within the range of, for example, compression TDC ± 10 °. If the stop crank angle Φstop is in the vicinity of the compression TDC, the stop position correction control in step S9 is performed. Run. That is, the stop position correction control is performed only when the crankshaft 114 is stopped near the compression TDC, which is the peak of pumping energy when the engine is stopped. Even in this case, the K0 clutch 34 is frictionally engaged by the stop position correction control. As a result, the crankshaft 114 is rotated from the vicinity of the compression TDC and is stopped within the target stop range Φtarget in combination with the pumping action, and the ignition start is appropriately performed at the next engine start and the assist torque is increased. The same effects as those of the above-described embodiment can be obtained, such as reduction.

  As mentioned above, although the Example of this invention was described in detail based on drawing, these are one Embodiment to the last, This invention is implemented in the aspect which added the various change and improvement based on the knowledge of those skilled in the art. be able to.

  10: Hybrid vehicle 12: Direct injection engine 34: K0 clutch 45: Electronic throttle valve (intake air amount adjustment valve) 58: Crank angle sensor 70: Electronic control device 80: Engine stop control means 82: Engine stop means 84: Throttle opening Means 86: Crank angle determination means 88: Clutch engagement means 100: Cylinder 114: Crankshaft MG: Motor generator (rotating machine) Φ: Crank angle Φtarget: Target stop range

Claims (6)

A direct injection engine having a plurality of cylinders and directly injecting fuel into the cylinders;
A clutch for connecting and disconnecting the direct injection engine to the power transmission path;
A rotating machine that functions as at least an electric motor;
The direct injection engine and the rotating machine can be used as a driving force source for traveling, and fuel is injected into the cylinder in which the piston is stopped in the expansion stroke while assist torque is applied by the rotating machine. In a hybrid vehicle in which an ignition start is performed to start the direct injection engine by injecting and igniting,
When the direct injection engine is stopped by disengaging the clutch during traveling, the stop position of the crankshaft is estimated based on the turning point that is the crank angle when the engine rotation speed becomes zero first, When the stop position deviates from a predetermined target stop range suitable for the ignition start, the pumping action is caused by the compression of air in the cylinder when the engine is stopped or immediately after the engine is stopped. With a connection torque that can disengage the crankshaft from the peak of pumping energy that occurs in the vicinity of the compression TDC in which the piston of any cylinder of the direct injection engine reaches the top dead center after the compression stroke within the time obtained , by temporarily connecting the clutch is cut off once, automatically the crankshaft in the crank angle to which the pumping energy is minimized area immediately after Engine stop control device for a hybrid vehicle, wherein the stopping the. The connection process of the clutch, the engine stop control device for a hybrid vehicle according to claim 1, wherein the crankshaft within the goals stop range is characterized in that it is determined to stop. The clutch engagement process generates a connection torque that can overcome the friction of the direct injection engine and rotate the crankshaft, and immediately disconnects the clutch when the crank angle exceeds a predetermined control stop position. The engine stop control device for a hybrid vehicle according to claim 1 or 2, characterized in that: The clutch connection process generates a connection torque that can overcome the friction of the direct injection engine and rotate the crankshaft for a predetermined period of time. An engine stop control device for a hybrid vehicle. The engine stop control device for a hybrid vehicle according to any one of claims 1 to 4 , wherein when the clutch is disconnected and the direct injection engine is stopped, an intake air amount adjustment valve is opened and controlled. The engine stop control device for a hybrid vehicle according to any one of claims 1 to 5 , wherein an output of the rotating machine is increased when the clutch is temporarily connected.

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